Process for cracking hydrocarbon oils



Original Filed Dec. 51. 1926 frn/enfom- Patented Oct. 24, 1933 UNITED STATES PATENT OFFICE Gustav Egloff, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota Continuation of application Serial No. 158,383, December 31, 1926. This application April 20, 1931. Serial No. 581,541

6 Claims. (01. 196-49 This application is a continuation of my application Serial No. 158,383, filed December 31, 1926, in turn a continuation in part of application No. 582,297, filed August 16, 1922.

This invention relates to improvements in a process and apparatus for cracking hydrocarbon oils and refers more particularly to the producing of low boiling point oil such as gasoline and the like, having a high percentage of unsaturated hydrocarbons. I 1 Among thesalient objects of the invention are to provide a process in which the oils are successively passed through zones of treatment serially connected, the successive stages or zones having increased pressures and temperature conditions to produce cracking in the oil introduced therein; to provide a process in which both the distillate and reflux condensate are retreated in order to extract the lower boiling point fractions therefrom.

The single figure is a diagrammatic side elevational view of the apparatus.

Referring to the drawing, the oil to be treated is introduced from any convenient extraneous source and is charged to the line 1 controlled by valve 2 to the still 3, which is mounted in a furnace 4 heated by gas burner 5. The vapors evolved are passed off through the line 6 regulated by valve 7 to a dephlegmator 8, while the residual substances are withdrawn as desired through the line 9 controlled by a valve 10. In the refluxing tower or dephlegmator 8 the oil is subjected to dephlegmating action, .the higher boiling point condensate being separated out and withdrawn therefrom through the line 11 regulated by a valve 12. This separated condensate which has a relatively higher boiling point than the vaporous products which rush into the top of the dephlegmator and pass off through the line 13, is charged by means of a pump 14 into the still 15 mounted above the furnace 16. In the still 15 the reflux condensate is subjected to increased temperature and pressure conditions whereby additional vaporization is eifected, the vapors rising from the still through the line 17 which is controlled by a valve 18 to a dephlegmator 19, the heavier liquid unvaporized constituents being drawn off through the line 20 from the bottom of still which is controlled by a valve 21. The vapors which withstand the condensing action in the dephlegmator .19 rise through the line 22 which is controlled by valve 23 and may be charged by means of a pump 24 at increased pressures to a final condensing stage not shown, connected to the discharge side of the pump 24 mounted in a furnace 29 and the vapors evolved therein pass off through the line 30 in which is interposed the valve 31 to the dephlegmator 32.

.The residual substances from the still 28 may be drawn oil through the valve 33 from the bottom of the still. The reflux oil separated out in the dephlegmator or refluxing stage 32 passes down through the line 34 regulated by a valve 35 and is charged by means of a pump 36 through the line 37 to a charging line 38, communicating with the still 40 which is mounted in a furnace41. In a like manner the reflux condensate withdrawn from the dephlegmator 19 fiows down through the pipe 42 and is charged by means of a pump 43 to the still 40 where it is combined with the condensate supplied thereto from the dephlegmator 32, hence the combined reflux condensates from the two dephlegmating stages are charged to the common still 40 and are there subjected to the increased temperature and pressure conditions to effect further conversion. The vapors evolved from this final stage pass off through the line 44 controlled by a valve 45 and rise through the dephlegmator 46 in which they are subjected to a refluxing action. The condensate separated out in the dephlegmator 46 is drawn off through the line 4'7 in which is interposed a valve 48 and is charged by means of a pump 49 to a zone of further conversion or directed to storage. The vapors, on the other hand, rising to the top of the dephlegmator pass oii through the line 50 and are charged by means of the pump 51 to a final condensing stage not shown where the ultimate distillate is liquefied, being subsequently collected in a receiving tank or reservoir also not shown, but familiar to the cracking art. In a like manner the vapors rising through the dephlegmator 32 are passed off through a line 52 regulated by a valve 53 and are charged to a condensing stage, not shown, Where they are subjected to a condensing action at an increased pressure by the pump 54. A residuum line 55 controlled by a valve 56 is supplied to the final still 40 and furnishes a means for withdrawing the residual unvaporized products therefrom.

The advantages of treating oil in this manner is the fact that a distillate having a higher percentage of unsaturates 'may be obtained where the oil is successively treated to reconversion in stages of increased temperatures and pressures. It is common knowledge that a reflux condensate separated out during the initial dephlegmation in a cracking system is a more refractory oil to crack than charging stock and must be subjected to increased temperature and pressure conditions to produce further conversion by successively treating both the distillates and reflux condensates in successive stages in the manner shown, a relatively complete conversion or cracking may be effected and an improved distillate obtained. By treating midcontinent gas oil of approximately 30 Baum gravity and subjecting it in the initial stage to a temperature of 720 F. and a pressure of 100 pounds, then retreating the reflux condensate in a secondary zone of treatment at a temperature of 740 and a pressure of 250 pounds, and simultaneously therewith treating the vaporous constituents passing over the top of the primary dephlegmator in a separate zone of conversion to a temperature of 760 and a pressure of 400' pounds, and in a like manner charging the reflux condensate from the vapors relieved from the two secondary zones of treatment in a final stage to temperatures ranging from 760 upwards and pressures of from 600 to 800 pounds, there may be obtained a high quality distillate having a gravity of approximately 65 Baum and containing 30% by volume unsaturates based on the raw charge as determined by the H2804 method. It will be understood that each still is equipped with a thermometer and that the temperature therein is regulated by the application of heat from the respective furnace. It is obvious that these temperature and pressure conditions will vary with the character of the oil used in order to produce the most advantageous conditions for conversion. The functioning of the separated stages may be controlled by the valves interposed in the lines to regulate pressures so that the most efiicient operating pressure may be used in the separate stages. The process is preferably operated continuously and the provision for withdrawing the residual substances from the separate stills will permit operation over a relatively long period of time.

The utility of this invention of subjecting reflux condensate from each still to increased pressure and temperature lies in the fact that each time an oil is subjected to cracking conditions it produces, in addition to the gasoline formed, a reflux condensate which becomes increasingly diflicult to crack under the same conditions of temperature and pressure from which it was formed. Further, the reflux condensate is a narrower boiling point fraction than the charging stock, or lends itself particularly to cracking at higher temperature and pressure from which it is formed due to it being more refractory than the stock from which it was produced.

The reflux condensate from the second cracking of the reflux obtained from the original charging stock calls for a high temperature and pressure to convert it into high anti-knock motor fuel. The reflux condensate obtained from the third cracking of reflux condensate calls for a higher temperature and pressure than the previous to produce even a higher anti-knock property gasoline than the previous one.

The same principle as just enunciated on the reflux condensate applies to the cracked distillates, particularly in reference to those containing a high percentage of sulphur, for the reason that each cracking breaks down the sulphur compounds to HzS, yielding a practically free sulphur content cracked gasoline. It has been found that high sulphur cracking stocks such as those produced from California and Mexico yield gasolines having a sulphur content of 0.6 to over 1.0% and it is costly to chemically treat the cracked product so as to produce a 0.1% commercial sulphur containing gasoline. Hence my process does away with the chemical treatment of cracked distillates due to the fact that the sulphur hydrocarbon compounds are broken down to hydrogen sulphide by re-treating the cracked distillates a number of times by means of the teachings of my patent application.

My intention covers broadly the re-cracking of reflux condensate produced by cracking the original charging stock and the subsequent re-cracking of reflux condensate produced from an earlier cracking operation and likewise subjecting the cracked distillate vapors produced from each stage of my process to higher temperature and pressure conditions to produce a high anti-knock motor fuel and a desulphurized gasoline.

Having thus described my invention, what I claim is:-

1. A process for producing gasoline of high anti-knock value which comprises subjecting heavy hydrocarbon oil to cracking conditions of temperature and pressure and, separating the evolved vapors from unvaporized oil, dephlegmating the vapors to condense and separate insufliciently cracked fractions thereof from the gasoline vapors, retreating resultant reflux condensate under cracking conditions of temperature and pressure, heating the dephlegmated gasoline vapors independently of saidheavy oil and reflux condensate to a temperature adequate to form substantial amounts of condensible unsaturated hydrocarbons therein, and condensing the thus heated gasoline vapors as a product of 115 the process.

2. A process for producing substantially sulphur-free gasoline of high anti-knock value from sulphur-containing hydrocarbon oil which comprises subjecting the sulphur containing oil to cracking conditions of temperature and pressure, removing resultant sulphur-contain-. ing and gasoline-containing vapors, dephleg-Q mating said vapors to condense and sep-v arate fractions thereof heavier than gasoline from the sulphurous gasoline vapors, retreating resultant reflux condensate under cracking con-' ditions of temperature and pressure, heating the dephlegmated gasoline vapors independently of said sulphur-containing oil and reflux condensate to a temperature adequate to form condensible unsaturated hydrocarbons therein and to break down the sulphur compounds contained therein to hydrogen sulphide, and condensing the thus heated gasoline vapors as a product of the process. 135

3. A process as defined in claim 1 further characterized in that the heating of said dephlegmated gasoline vapors is efiected under higher pressure than is the cracking of said heavy oil.

4. A process for producing gasoline of high 140 anti-knock value *which comprises subjecting heavy hydrocarbon oil to cracking conditions of temperature and pressure and separating the evolved vapors from unvaporized oil, dephlegmating the vapors'to condense and separate insufll- 145 ciently cracked fractions thereof from the gasoline vapors, retreating resultant reflux condensate independently of and under more drastic cracking conditions than said heavy oil thereby forming additional gasoline vapors, heating the 150 7 form condensible unsaturated hydrocarbons acterized in that the heating or said first menized oil, fractionating the vapors to form a reflux fraction heavier than gasoline and a lighter fraction comprising gasoline hydrocarbons, retreating resultant reflux condensate under cracking conditions or temperature and pressure, directly passing said lighter fraction comprising gasoline hydrocarbons separated by the fractionation to a secondary zone and there heating the same in vapor phase to higher cracking temperature and under higher pressure than said charging oil to form condensible unsaturates therein, condensing the vapor phase heated lighter traction, and collecting the resultant gasoline-containing condensate as a product of the process.

first mentioned gasoline vapors sufllciently to therein, and condensing the thus heated gasoline vapors and said additional gasoline vapors as products of the process.

5. A process as defined in claim 4 further chartioned gasoline vapors is eflected under higher pressure than is the cracking of said heavy oil and reflux condensate.

6. A process for producing anti-knock motor fuel which comprises heating hydrocarbon charging oil to cracking temperature under superatmospheric pressure of at least one hundred pounds per square inch in a primary zone, separating the heated oil into vapors and unvapor- GUSTAV EGLOFF. 

